1. Field of the Invention
The present invention relates to a computer controlled system for an industrial process and, more particularly, to a computer controlled system for an industrial process in which interactive control by a human operator is achieved through a touch-responsive visual display.
Many system-type industrial installations, for example, those related to industrial process-type manufacturing and electrical power generation, employ a larger number of physically distributed controlled devices and associated sensors for effecting coordinated operation of the overall system. In the past, coordinated control of various devices has been achieved by manual operation and various types of semi-automatic and fully automatic control systems including electromagnetic relay systems, hard-wired solid state logic systems, and various types of computer controlled systems. The computer systems have included central systems in which the various sensors and controlled devices are connected to a central computer, distributed control systems in which a remotely located computer is connected to each of the controlled devices and to one another, and hybrid system combinations of the central and distribution systems.
In the computer-type control system, the man/machine interface has been typically accomplished with a cathode ray tube (CRT) visual display device in combination with a standardized keyboard. To effect the entry of a command, the system operator usually must enter a code, such as an alpha-numeric acronym or mnemonic, and then enter another code for the command to effect the requested information display, change in the operation of the controlled device, and/or change the set point of a system parameter. Because the entry of this type of information requires correct depression of a sequence of key pads, keyboard entry of commands is dependent upon the skill of the system operator and is, of course, subject to error. The error rate inherent in this type of information and command entry has been recognized in the art and has given rise to often sophisticated entry verification programs by which an invalid entry will be recognized and an appropriate "invalid message" will be displayed to permit the operator to re-enter the message in correct form. While these types of validity checking programs are effective for the detection of mis-struck key pads in making alpha-numeric acronym or mnemonic entries, they are of no assistance when the system operator correctly enters an unintended mnemonic, e.g., when the operator intends to change the operational state of a pump but absentmindedly enters the correct mnemonic for a change in the operation of a compressor. The entry validity checking program will usually not detect this type of error.